T Law

The Future of Thermal Comfort in an Energy- Constrained World

In the context of global warming the sum of current trajectories, known as the business as nusual scenario, is generally compared unfavourably to alternative low-carbon scenarios. nOne of these trajectories sees the continuation of an unabated demand for air-conditioning nwith its inevitable increase in energy consumption. This thesis proposes strategies to nameliorate this problem in the difficult context of a knowledge-based economy in an nequatorial climate. nIt begins by retracing the emergence of thermal comfort standards in consumer societies, ntypified by the pursuit of individualistic interests. It identifies a gap that can explain why nthe scientifically valid adaptive comfort standard has not stemmed the continuous growth nin air-conditioning demand, especially in knowledge-based economies. It is proposed that nthe nexus is brain cooling and while some studies have acknowledged, it has been too ncomplex to quantify in existing comfort models. With the high variability of individual ncomfort demands, this thesis argues that future provisions of thermal comfort will be nachieved by facilitating personal control over the microclimate. nA number of innovations are explored through cycles of action research, and the underlying nproblems are then crystallised. A successful innovation has to appeal to the business ninterests of key decision makers, conform to consumer interests of improved thermal ncomfort and address the need to conserve energy. nThis has led to the development of a whole building solution (the Rain Tower), a floor-by-floor napproach (a desiccant wheel AHU) and finally, cooling by means of a personal air-conditioning nsystem called the Ductless Task Air-Conditioning (DTAC) system. The DTAC ntechnology, meeting the criteria for commercialisation, was subsequently prototyped and nits performance measured. Further refinements were made before undertaking a pilot study nto field trial the system in naturally ventilated offices and a climate controlled room. The nresults are analysed statistically to quantify its improvement to sensation and comfort. nWhilst this thesis emerges from an architectural science platform with a primary interest in nthermal comfort, it draws on the disciplines of engineering, sociology, physiology and nbusiness to frame and propose viable solutions to this complex real world problem. nThis thesis studies the behaviours that persist in the business-as-usual scenario and the nreasons for the difficulties in changing attitudes. Technologies are then developed to reduce nthe environmental impact of air-conditioning whilst conforming to current and future nexpectations of thermal comfort. nThe results of the research demonstrate that thermal comfort, with reduced carbon nemissions compared with conventional air-conditioning, can be provided for workers in nknowledge-based economies in hot humid equatorial climates.

Literature Review: Thermal Comfort and Air-Conditioning

The cost of supplying energy to the office space has historically been insignificant compared to the cost of labour. A study on a typical American office (Holz et al. 1997) found the cost of salaries to be 100 times more than that of energy. In Singapore, the electrical consumption of offices accounts for 12 % of the overall non-manufacturing sector’s usage, with an average annual energy efficiency of 231 kWh/m2 (Lee 2001). In an ongoing study by the Energy Sustainability Unit in Singapore (esu.com.sg) the median office building uses 49 % of its energy on air-conditioning and a further 14 % on mechanical ventilation.

The Unintended Consequence of Building Sustainably in Australia

What makes a sustainable house? One might suggest it should be energy-efficient, resilient to climate change and still comfortable. Indeed in Australia, we see aspects of these three priorities being exercised: energy-efficiency standards being introduced into residential requirements of the National Construction Code in 2003, bushfire requirements expressed as a national standard in 2009, and the constant demand for more efficient and round-the-clock climate control. All these actions relate to Sustainable Development Goal (SDG) 13: Climate Action. One might assume that these trends mark progress for both the environment and the home owners. However there is a dark side to the story, because in the very effort of reducing greenhouse gas emissions (also one of the functional objective of the national construction code), the construction industry has inadvertently implemented practices that have led to entrapment of moisture in buildings, thus compromising their habitability. Using data from Tasmania, this chapter shows how common mistakes in building science, design and construction have led to a widespread increase of condensation in buildings located in cool climates. Condensation has further led to other problems with mould and health (SDG 3: Good Health and Well-being), making new code-compliant houses potentially uninhabitable after experiencing their first winter. These challenges need to be in the wider discussion of architecture, construction, indoor microbiology and public health when sustainable housing standards are being promoted.

Comfort Energetics: Thermal Comfort Under Energy Constraints

This chapter represents an energy-conscious approach to understanding thermal comfort. With the environmental variable of T, MRT, RH and wind v as its structure, it begins with a psychrometric analysis where the roles of temperature and humidity are denominated in PMV votes and the power needed to improve those votes. The role of humidity is critically reviewed with a case made for challenging the accepted norms an optimum RH range. Finally the efficacy of moving air is analysed in the different ways it can be employed.

Appendix: Building and Optimising the DTAC

This appendix explains how the DTAC was developed and optimised in a step-wise process. The advances have been categorised by the components (instead of chronologically) for clarity.

Field Testing DTAC, Methodology and Results

The Ductless Task Air-Conditioning (DTAC) system was developed for supplementary personal cooling to office occupants. DTAC utilised thermoelectric (peltier) modules for heat exchange into a phase change material (PCM) as heat sink, allowing workspaces to be air-conditioned with no installation. The process of prototyping and optimising this unit is covered at length and in detail in Appendix.

The Rain Tower

Rather than tinkering with small incremental improvements in the efficiency of air conditioning systems, we need a step change to new paradigms for cooling buildings. Just as with the cars, we need super-low-consumption, dual fuel, eco-buildings that are naturally ventilated in spring, winter and autumn, and in summer are run on solar air conditioning when the sun is out topped up by small amounts of grid electricity when it is not. This is the way forward. (Roaf 2005, p. 233)

Personal Air-Conditioning

Majority of air-conditioned offices rely on total volume air distribution (TVAD) to attain a fairly homogenised mix of fresh and recirculated air, supplied at temperature and velocity that would satisfy most occupants.

Finding a Market-Oriented Solution

In the previous chapter, a design methodology had emerged for the innovation process: n n nUsing a design brief instead of an academic research question. n n nAdopting an action research cycle to improve the ideas: plan → act → observe → reflect → plan… n n nUtilising the architectural studio model of the critique as reflection, which involved: n n nself-critique, and n n nsupervisors’ critique.

The State of the World

In the fourth assessment report of the UN Intergovernmental Panel for Climate Change (IPCC), the robust finding (defined as that which ‘holds under a variety of approaches, methods, models and assumptions, and is expected to be relatively unaffected by uncertainties’ (IPCC, 2007, AR4 SYR - Topic 6)) was that ‘warming of the climate system is unequivocal,’ and that ‘most of the global average warming over the past 50 years is very likely due to anthropogenic Green House Gases (GHG) increases’ (IPCC, 2007, AR4, 6.1). The IPCC also identified the building industry as the one with the most climate mitigation potential (Table 2.1). When Time Magazine (Kluger, 2007) ran a special feature called The Global Warming Survival Guide, buildings accounted for the largest share of U.S. emissions, noting that: